1. Field of the Invention
The present invention relates to a door locking handle assembly used in a plugboard box and the like for opening/closing a door of the box and for locking the door to a stationary frame of the box.
2. Description of the Prior Art
In a conventional door locking handle assembly such as one disclosed in Japanese Utility Model Laid-Open No. Sho 63-162075: a locking shaft of a handle piece is rotatably mounted in a cylindrical bearing portion of a base member which is fixedly mounted on a door; a catch plate, which is engaged with and disengaged from a retaining member of a stationary frame, is fixedly mounted on a front-end portion of the locking shaft; and, when the handle piece is swung on the cylindrical bearing portion, the catch plate is rotatably driven between its locked and unlocked position. The catch plate projects from a side edge portion of the door in its locked position, and retracts to a predetermined position behind the side edge portion of the door in its unlocked position.
In the conventional door locking handle assembly: as a means for locking the door to the stationary frame in the locked position of the door, a lock unit is provided in the locking shaft of the handle piece; and, a front-end portion of a rotor of the lock unit is interlocked with a locking rod which is engaged with and disengaged from a receiving groove of the cylindrical bearing portion when the rotor is rotatably driven.
However, in the conventional door locking handle assembly, there is a fear of deforming both the locking rod and an internal locking mechanism of the lock unit when the lock unit is illegally unlocked by persons who grip the front-end portion of the handle piece and forcibly swing the handle piece without using a proper key, because the elongated body of the handle piece acts as an arm of a lever in such illegal operation to multiply the force on the handle piece several fold and the thus multiplied force produces large bending and shearing stresses in both the locking rod and the internal locking mechanism of the lock unit.
Further, in the conventional door locking handle assembly, since it is possible for the user to normally operate the lock unit even when the handle piece is not in its normally locked position, there is a fear that the user overlooks such unlocked condition of the handle piece.